1. Field of the Invention
The invention relates to preparations for treating fibers, such preparations being especially suitable as finishing agents for synthetic fibers obtained from melt spinning and especially polyester fibers thus prepared.
2. Description of the Prior Art
Polydimethylsiloxanes are used in spinning plants for finishing melt-spun fibers. This use becomes possible because of the fact that polydimethylsiloxanes, which generally are referred to simply as silicone oils, endow the treated fibers with a low coefficient of friction, especially at high yarn-take-off rates, whereby this coefficient has only a slight temperature dependence. In addition, silicone oils are unusually heat stable and have a low viscosity-temperature coefficient.
The finishing of melt-spun yarns directly after their manufacture makes possible the subsequent drawing and texturizing processes. The finish must be effective both as a lubricant and as an antistat. In the thermal fixation processes to which the yarn is subjected, components of the finish are flung off onto the heating unit where they are exposed to heat for a long time. For this reason, the finish must be thermally stable. Those parts of the finish which are deposited on the heating units should, as far as possible, not yellow or evaporate, and most importantly, not gel. At the same time, the constituents of the finish should be as compatible as possible with one another. This is a problem especially when it is important to have compatibility between the polar, surface active components, which are responsible primarily for the antistatic effect, and the nonpolar methylsilicone oils which are responsible primarily for the lubricating properties.
The compatibility of methylsilicone oils can be improved, if methyl groups are partially replaced by longer chained alkyl groups. The resulting oils are then, however, no longer sufficiently thermally stable. In addition, the viscosity-temperature coefficient of methylsilicone oils, modified in such a manner, increases greatly.
Even the partial replacement of methyl groups by phenyl groups leads to products with higher viscosity-temperature coefficients whose lubricating properties are impaired.